Assessing microbial residues in soil as a potential carbon sink and moderator of carbon use efficiency
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Assessing microbial residues in soil as a potential carbon sink and moderator of carbon use efficiency Kevin Geyer Serita Frey
. Jo¨rg Schnecker
. A. Stuart Grandy
. Andreas Richter
.
Received: 3 June 2020 / Accepted: 30 October 2020 Ó The Author(s) 2020
Abstract A longstanding assumption of glucose tracing experiments is that all glucose is microbially utilized during short incubations of B2 days to become microbial biomass or carbon dioxide. Carbon use efficiency (CUE) estimates have consequently ignored the formation of residues (non-living microbial products) although such materials could represent an important sink of glucose that is prone to stabilization as soil organic matter. We examined the dynamics of microbial residue formation from a short tracer experiment with frequent samplings over 72 h, and conducted a meta-analysis of previously published glucose tracing studies to assess the generality of these
Responsible Editor: Susan E. Crow.
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10533-020-00720-4) contains supplementary material, which is available to authorized users. K. Geyer (&) A. S. Grandy S. Frey Department of Natural Resources and the Environment, University of New Hampshire, Durham, NH 03824, USA e-mail: [email protected]
experimental results. Both our experiment and metaanalysis indicated 30–34% of amended glucose-C (13C or 14C) was in the form of residues within the first 6 h of substrate addition. We expand the conventional efficiency calculation to include residues in both the numerator and denominator of efficiency, thereby deriving a novel metric of the potential persistence of glucose-C in soil as living microbial biomass plus residues (‘carbon stabilization efficiency’). This new metric indicates nearly 40% of amended glucose-C persists in soil 180 days after amendment, the majority as non-biomass residues. Starting microbial biomass and clay content emerge as critical factors that positively promote such long term stabilization of labile C. Rapid residue production supports the conclusion that non-growth maintenance activity can illicit high demands for C in soil, perhaps equaling that directed towards growth, and that residues may have an underestimated role in the cycling and sequestration potential of C in soil. Keywords Carbon use efficiency Isotopic glucose tracing Carbon cycling Microbial ecology Microbial residues
K. Geyer Department of Biology, Young Harris College, 1 College St, Young Harris, GA 30582, USA J. Schnecker A. Richter Centre for Microbiology and Environmental Systems Science, University of Vienna, 1090 Vienna, Austria
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Biogeochemistry
Introduction As the largest pool of carbon (C) in the biosphere, soil organic matter (SOM) and its transformation represent a critical component of global C cycling. Carbon entering the soil is primarily plant-derived but subsequent processing relies heavily on microorganisms. Microbial decomposition and metab
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